LED (Light Emitting Diode) elements as a semiconductor light source are widely used for a vehicle light, a traffic light, and an illumination light. In such purposes, since the light emission amount of a single LED element is small, it is general to light a plurality of LED elements simultaneously, to obtain a required light emission amount.
In a conventional LED lighting device, a converter is connected in series to an LED unit composed of one or a plurality of LED elements connected in series, and further, a single DC power supply is connected to both ends of an LED circuit block composed of the LED unit and the converter. The converter is composed of a switching element, a diode, and a reactor, and constant current control is performed for current flowing in the LED unit by turning on or off the switching element, thereby lighting the LED unit. In addition, a plurality of the LED circuit blocks are connected in parallel to the DC power supply, and the plurality of LED circuit blocks are operated by a single DC power supply (for example, Patent Document 1).